AppliedSensor Provides Hydrogen Detection Sensors for BMW Hydrogen 7

17 March 2007

The HS-440 hydrogen sensor.

AppliedSensor’s HSS-440 hydrogen gas detection module is incorporated in the BMW Hydrogen 7, being built by BMW in a limited series and deployed to selected users in the US and other countries. The BMW Hydrogen 7 features a dual-mode drive system fueled either by a 19.5-gallon gasoline tank or a 17.6-pound liquid hydrogen tank. (Earlier post.)

The AppliedSensor HSS-440 module incorporates high-performance sensing based on advancements in Field Effect (FE) technology designed specifically for fuel cell and hydrogen-powered vehicles. The modules are mounted in the car cabin, under the hood and in the trunk area to detect hydrogen gas leaks at levels below the established lower explosion limit of four percent in-air.

The FE sensor technology is based on the field effect generated by gases in metal oxide semiconductor field-effect transistor (MOSFET) devices with catalytic metals. The charging of the gate contact by the gas molecules results in a voltage change in the sensor signal. The choice of operation temperature, gate metal, and structure of the gate metal determine the selectivity of the gas response.

FE sensors respond to gases like hydrogen, ammonia, amines, ethanol, acetone, hydrocarbons, CO, and NO2. The sensitivity of the sensors is normally high for low concentrations of the gases, while it becomes saturated for high concentrations of the gases.

The HSS-440 incorporates a field-effect transistor with a catalytic metal gate stack as the gas-sensing layer. Hydrogen molecules interact with the gate thereby changing characteristics of the transistor. The sensor is fed by a constant current source and gives a voltage output proportional to the logarithm of the hydrogen concentration in the ambient.

reminds me of a project I worked on for automotive air conditioning using 8 0z 0f propane 9 (less than a dollar) to replace the r-134a ( a bit more).
r-134a has no chlorine (ozone hole) but very high GWP(global warming.
Too dangerous to have in a car said the government.
Only 20 gallons of "inert gas" in the fuel tank.
Oil companies say it is safe, so it is.
Chemical companies that make expensive refrigerants say propane is dangerous, so it is.
Most household refrigerators produced in europe use propane/butane type fluidsy.
PS If "They" did not want Freon (refrigerants) to leak they would add an oderant to notify the user.

The difference between a fuel system and an air conditioning system is that the air conditioning system must loop inside the passenger compartment. Assume a propane leak inside the passenger compartment, then assume that the driver has decided to light up a cigarette, or that a faulty relay creates an electrical arc.

Household refrigerators are not subject to the vibration cycles present in vehicles, nor are they mounted in such confined spaces. Propane and butane are popular in many parts of the world not because they are perfect, but because they displace greenhouse gas - producing refrigerants such as HFC-134, as you mentioned.

Gasoline is indeed a dangerous fuel, but your comparison does not illustrate that.

Hydrogen 7 is unique. While other manufacturers have developed fuel cell cars use hydrogen to create energy that powers an electric motor car BMW liquid hydrogen is burned directly in an internal combustion engine. It uses the same V12 engine to burn gasoline and hydrogen in a fuel tank for each - which is contrary to both body and space, the cockpit, but gives drivers the option of using clean combustion of hydrogen when they can find and gasoline goes from a hydrogen filling station.BMW Hydrogen19